Method of operating heat exchangers



May 1950 c. J. LOCKMAN 2,508,119

METHOD OF OPERATING HEAT EXCHANGERS Filed May 12, 1945 Ti /4 fie a Z0 56/5 Patented May 16, 1950 METHOD OF OPERATING HEAT EXCHANGERS Carl JohanLockman, Enebyberg, Sweden, as-

signor, by mesne assignments, to Rosenblad Corporation, New York, N. Y.,a corporation of New York Application May 12, 1945, Serial No. 593,457In Sweden June 5, 1944 3 Claims.

The present invention is concerned with the operation of heat exchangerswith two separate channel systems and has particular reference to suchcases in which one of the heat exchanging fluids may cause incrustationof the heat transmitting walls while the other fluid is capable ofdissolving and removing the incrustations as, for instance, when usingcondensing steam or hot water which in most cases constitute the otherIn such case it is known to clean the heat exchanger, practicallywithout interrupting the heat exchange process, by passing differentfluids alternately through the respective channel systems so that thechannel system which has conducted the crust forming fluid during oneperiod, will during a subsequent period conduct the crust dissolvingfluid, which will remove the incrustations formed during the previousperiod, if the alternations of fluids are suitably timed.

It has, however, been observed that the incrustation will generally growconsiderably faster and thicker than elsewhere at the hottest part ofthe channel systems which is mostly at the top or the bottom where theheat delivering fluid is generally admitted. This is obviously aconsiderable drawback in as much as it requires more frequentalternations of fluids than if the encrustation were more evenlydistributed. However, a short cycle is undesirable because thealternation of fluids involv some loss of time and fluids and shouldtherefore take place as seldom as possible.

Furthermore, when the heat delivering fluid consists of condensingsteam, as is most frequently the case, the cleaning efiect thereof uponthe incrustations will be considerably less than the average in theneighborhood of the inlet opening for the steam, which is normally atthe top or bottom part of the channel systems because it is actually thecondensate which is active in dissolving the crust deposits andnecessarily there will be but little condensate present near the steaminlet and accordingly the cleaning effect in that zone will be ratherslow whereas it increases as the flow of condensate increases towardsthe discharge end of the channel system. The consequences thereof willbe exactly the same as above stated to be caused by the uneven thicknessof the crust deposits and thus the difficulty will be doubled.

It is an object of the present invention to overcome the imperfectionsmentioned so as to reduce the frequency of alternations of fluids and toperform this by turning over the heat exchanger at suitable intervals soas to cause its top and bottom portions to change places.

According to the invention the turning of the heat exchanger may takeplace at any suitable moment, either simultaneously with alternation 2of fluids between the channel systems or independent thereof and betweentwo subsequent alternations and possibly at intervals between repeatedalternating periods.

Suitably the heat exchanger to be subjected to the present operatingmethod should be made symmetrical in order to facilitate the differentprocedures and measures required therefor, and further it should beprovided with horizontally disposed supporting pivots fitted in bearingsand connected, for instance, with a suitable gearing for turning theapparatus.

The invention will be further illustrated by three embodiments ofapparatus for carrying out the same which are shown in the accompanyingdrawing, of which Fig. 1 is a more or less diagrammatic view, partiallyin cross-section, of one form of heat exchanger arrangement suitable forcarrying the invention into effect;

Fig. 2 is a view showing the exchanger of Fig. 1 in reversed position;

Fig. 3 is a view similar to Fig. 1 showing another embodiment of theinvention; and

Fig. 4 is a view similar to Fig. 1 showing still another embodiment.

In the drawing the numeral l designates the heat exchanger being in thiscase a common tubular apparatus with the heat transmitting surfaceformed by a set of tubes 2. The apparatus is carried by the pivots 3 sothat it can be rotated around an horizontalaxis through the centre ofgravity by means of gearing 4.

In the position shown the apparatus is supplied with heating steamthrough the inlet connection 5 to the conduit l0 communicating with thechannel system formed outside the tubes and therefrom the condensate isdischarged through the conduit I I to the outlet connection 6, whereas acrust forming liquid to be heated is introduced from the inletconnection I to the conduit I2 communicating with the channel systemformed inside the tubes and leaves the same through the conduit l3 tothe outer connection 8. Under such circumstances the highest temperatureof the heat transmitting surface will prevail at the upper portion andin that zone therefor the crust deposits will grow more rapidly andthicker than elsewhere while the cleaning effect will be comparativelyweak in the same zone for reasons referred to above. To compensate forthis in accordance with the invention the apparatus is at suitableintervals turned over after interrupting the flow of fluids andloosening the connections 5, 6, I and 8, and this being done theconnections 5, 6, I and 8 are again attached to the conduits l2, l3, l0and II, respectively, as shown in Fig. 2. Then each fluid will beconducted through the other of the channel systems as compared with theprevious position shown in Fig. 1, so that any crust deposits formed bythe liquid on the inside 01' the tubes during the former period will bedissolved and removed by steam and condensate within the tubes during asubsequent period. Such operating cycle may be repeated any desirednumber of times, and by suitable timing the turning of the apparatus andalternation of fluids between the channels the transmitting surfaceswill be maintained substantially clean in a very practical and efllcientmanner. I

In the embodiment shown in Figs. 1 and 2, reversal of the position ofthe exchanger will operate to simultaneously change or alternate theflow of the fluids through the different channel systems, but aspreviously mentioned this may not be essential or even desired and inFig. 3 an arrangement is shown in which reversal of position of theexchanger may be efiected independently of change of the fluids throughthe different channel systems. In this embodiment the construction ofthe exchanger is as previously described, but in this instance the inletconduit l and the outlet II for one fluid are on the same side of theexchanger, whil both the inlet conduit i2 and outlet conduit lit for theother fluid are on the opposite side of the exchanger. As will beevident from the drawing, reversal of the position of the exchanger willnot change the channel systems through which the respective fluids passbut will change the end of the exchanger at which the scale formation smost rapid and the end where its removal is most effective. For changingthe fluids from one channel system to another, suitable connections (notshown) are provided for supplying, as desired, either one or the otherof the fluids to the inlet conduits I0 and I2 respectively.

In Fig. 4 another arrangement is shown whereby the exchanger may beturned with or without simultaneous change in the flow paths of thefluids. In this arrangement the steam inlet conduit I0 may be connectedeither to the tube system through the conduit Illa or to the systemoutside the tubes through conduit lob, these conduits being controlled,respectively, by valves I4 and I5. Likewise the condensate conduit H maybe connected to either system through conduit Ha or I lb, these conduitsbeing controlled respectively by valves I6 and i1. Similarly, the flow0f the other fluid from the inlet conduit II to the outlet conduit [3may be directed through one or the other of the channel systems via theconduits I 2a and I 2b, controlled respectively by valves [8 and I9, andconduits Ila and lib controlled respectively by valves 20 and 2|. If,for example, with valves I5, I], I 8 and 20 open and valves I4, l6, l9and 2| closed, reversal of the exchanger without changing the valveswill not change the channel systems through which the respectiv fluidsflow. On the other hand, opening the closed set of valves and closingthe open set will operate to change the flow of the fluids to thealternate channel systems. Obviously reversal 0f the exchanger andchanging of the setting of the valves may be made independentl of eachother or concurrently to secur any desired cycle of operation. While inall the embodiments shown by way of illustration rigid pip connec- Iters Patent is:

tions have been shown, it will be evident that flexible connections maybe employed in case it is desired to, reverse the exchanger withoutinterruption of fluid flow.

Naturally the invention is not confined to the 1. A method of operatingheat exchangers with two separate channel systems in heat exchangerelation, comprising the steps of passing an encrustation depositingfluid through one channel system, passing a vaporous fluid which forms ascale removing condensate through the other channel system from the topto the bottom end thereof, alternating the channel systems through whicheach fluid flows, and turning over the heat exchanger at suitableintervals so as to cause its top and bottom portions to change places,said vaporous fluid being after such a turning over operation enteredinto either channel system at its top end which constituted its bottomend before said turning operation.

2. A method of operating heat exchangers with two separate channelsystems in heat exchange relation, comprising the steps of passing anencrustation depositing fluid through one channel system, passing avaporous fluid which forms a scale removing condensate through the otherchannel system from the top to the bottom end thereof, directing theflow of each fluid during subsequent periods first through one and thenthrough the other channel system, turning over the heat exchanger at anydesired moment of such a flow period so as to cause its top and bottomportions to change places, and maintaining the same flow through thesame channel systems with unchanged flow directions immediately beforeand after the turning over operation, whereby said vaporous fluid willon entering from the top into the respective channel system be receivedalternately at opposite ends thereof.

3. A method of operating heat exchangers with two separate channelsystems in heat exchange relation, comprising the steps of passing anencrustation depositing fluid through one channel system, passing avaporous fluid which forms a scale removing condensate through the otherchannel system from the top to the bottom end thereof during a selectedperiod of time, alternating the channel systems through which each fluidflows during subsequent periods between any consecutive such flowperiods, interrupting the flow while turning over the heat exchanger soas to cause its top and bottom portions to change places, and thenre-admitting the flow but changing the paths of each fluid from one tothe other channel system, said vaporous fluid being thereafter receivedinto the respective channel system at the end thereof which has beenmoved from bottom to top position.

CARL JOHAN LOCKMAN.

REFERENCES CITED The following references are of record in the flle ofthis patent:

UNITED STATES PATENTS Number Name Date 1,006,197 Frasch Oct. 17, 19111,464,705 Goosmann Aug. 14, 1923 2,188,245 Middleton Jan. 23, 19402,380,604 Melton July 31, 1945

